For the marinade: Whisk the yogurt, cilantro, tomato paste, ginger, lemon juice, brown sugar, coriander, cumin, turmeric, cardamom, chili powder, garlic and salt and pepper together until well blended.
For the skewers: Thread the pieces of salmon and peppers onto the skewers, using 5 pieces of salmon for each skewer and 4 each of the peppers, alternating them so the peppers are between the pieces of salmon. Place them in a dish that will accommodate them in a single layer and pour over the marinade. Turn the skewers a few times, making sure they are well coated, cover with plastic wrap and place in the refrigerator to marinate for at least 1 hour.
Preheat an indoor grill or a barbeque grill to medium-high heat. Oil the grill, remove the skewers from the marinade and sprinkle them with salt. Place on the grill and cook about 5 minutes, turning halfway through cooking. Skewers are done when the fish is firm and slightly charred.